MAZDA- SKYACTIV CHASSIS
SKYACTIV-CHASSIS
In pursuit of the 'oneness between car
and driver' achieved in the MX-5, this lightweight chassis has improved comfort
and security, while at the sametime delivering Mazda's hallmark fun-to-drive
feel.
Features
of SKYACTIV-CHASSIS
・Suspension
and steering functions have been thoroughly revised to achieve the 'driving
pleasure of oneness between car and driver'
・Driving
quality has been raised to new levels through improvements to comfort and
security.
・Newly-developed
front and rear suspension systems and electric power steering.
Functional improvements are combined with reduced weight. The entire
chassis is 14%*
lighter than the previous model.
* Figures are for a CD-segment car (Mazda6 class)
Technical
Aims and Concept
（1）Combination of low-to mid-speed
agility and high-speed stability
（2）Balance of ride comfort with low-to
mid-speed agility
（3）Joint achievement of weight
reduction and excellent rigidity
The front and rear suspension have been redesigned to deliver low-to
mid-speed agility and high-speed stability, nimble yet high quality ride
comfort, with a light chassis and superior rigidity. A lightweight, highly
rigid cross member and electric power steering also contribute to quick
handling.
SKYACTIV-CHASSIS:Aims
of technology
Combination
of light feel at low-to-mid speeds and stability at high speeds
When the yaw gain (the force that turns a vehicle) is set at a high
level to enhance the car’s nimbleness at the low-to-mid speeds, it tends to
become excessive at high speeds, producing an oversensitive response in the
car’s movements. To resolve this issue, we re-examined the geometry of the rear
suspension. First of all, to ensure smooth movement at high speeds, we
optimized the suspension links, and increased the grip of the rear wheels in
response to impact (reducing the yaw gain).
fig.2:Vehicle
movement changes in accordance with speed
Next, to ensure nimbleness of movement at low-to-mid speeds, we adopted
a higher steering gear ratio (increasing yaw gain). By doing so, we
simultaneously increased yaw gain at low-mid speeds and reduced yaw gain at
high speeds, achieving improved nimbleness at the low-mid speed range and
greater stability at the high-speed range.
The next challenge was to deliver agility at low-to-mid speeds at the
same time as maintaining stability at high speeds, in terms of both vehicle
movement and the steering force required. In other words, this refers to
ensuring that the steering feel varies according to the speed of the vehicle.
First of all, to ensure firm steering at high speeds, the front
suspension caster angle and caster trail were increased to enhance
self-aligning torque. Next, to ensure light and smooth steering at low-mid
speeds, electric power steering controls were used to increase the power
assistance at low-mid speeds, thus making the steering lighter. In this way we
have created a steering feel that conveys security and a sense of oneness
between car and driver, while also matching the car’s movements.
fig.3:Increased
caster trail
Balance
of ride comfort with agility at low-mid range
The next aim was ride comfort the balance of agility with comfort. We
revised the structure of the suspension to improve handling without making the
springs and dampers stiff. First of all, to enhance the operational efficiency
of the dampers, the mounts were set at a position that enables a greater lever
ratio.
By implementing this change, damping force and the rigidity of the top
mount rubber could be reinforced, reducing the impact on ride comfort. The rear
suspension trailing link attachment position was also shifted upwards. In this
way, the direction of movement of the trailing links is adjusted to more easily
absorb longitudinal impact shocks from the road, contributing to improved ride
comfort. At the same time, as this also prevents the rear of the vehicle from
rising, the vehicle has increased stability when stopping, which helps to
reduce stopping distance.
Reduction
of rear suspension impact shock
Joint
achievement of weight reduction and excellent rigidity
~ Lightweight cross member with high
rigidity ~
To help to achieve the weight reduction target, we worked on the
optimization of the cross member (suspension member) structure and engineering
method. After first ensuring that the functionality requirements were met, CAE
technology was then used to create a concept model to develop the optimum
structure.
When doing so, we verified at the same time that this was coordinated
with the overall vehicle package. In the front, the center car section was
extended and the longitudinal offset of the lower arm attachment position was
reduced. In the rear, the longitudinal span of the cross member was extended
and the longitudinal offset of the lateral link attachment position was
reduced.
Welding flanges were also removed from the front and the rear, to
enhance the coupling rigidity of the welded sections. The structure thus
adopted achieves both weight reduction and superior rigidity, contributing to
the 14%* in weight reduction of the entire chassis, compared with current
models.
* Figures are for a CD-segment car
(Mazda6 class)
Comparison
of current and new cross members
